The present invention relates to conveyors, and in particular to a transport arrangement for loading semitrailers and the like from a dock area.
Large semitrailers and other similar cargo carrying vehicles are typically loaded from an elevated dock area of a warehouse or factory. In the grocery industry, the vehicles are capable of transporting more than one order at a time, so that the goods for each order must be loaded sequentially into the trailer in accordance with the selected delivery route. Overhead warehouse conveyors are generally used to transport the unpalletized articles of each order from a warehouse area to a loading area of the facility. The articles are manually lifted off of the conveyor and stacked onto pallets to facilitate unloading. Large, bulky items, such as paper goods and the like, are already palletized by the manufacturer, or are batch picked, and are loaded directly into the trailer by a hand truck or fork lift vehicle.
Telescoping conveyors, such as that illustrated in U.S. Pat. No. 3,294,214, have been used to transport articles from a loading dock into a trailer or truck bed. However, such conveyors have either a rather complicated, two-part conveyor belt arrangement, and/or must be cantilevered into the trailer from the loading area. This type of construction is generally considered inherently unstable, and is particularly unwieldly for loading long semitrailers.
The bays in loading docks are rather narrow, and spaced closely together in a side-by-side fashion, such that it is important to provide trailer loading conveyors with a mechanism which not only aligns the conveyor with the trailer, but can also guide the conveyor into a preselected storage position. Heretofore, the telescoping, cantilevered type of extendable conveyors have included channels or tracks in the floor of the loading dock which extend to the dock plate to guide the conveyor between the extended and retracted positions. However, the tracks and mating caster wheels are subject to abuse and deterioration from vehicular traffic, such as fork lift trucks, hand trucks, dropped loads, foreign materials, and the like. The conveyors themselves are also subject to damage from collisions with fork lift trucks and other traffic. Hence, such conveyors can quickly become difficult to operate, and require frequent repair.
Another drawback associated with the telescoping type of conveyor is that it cannot be steered or moved laterally in the loading bay. As a result, such conveyors must be positioned along the longitudinal centerline of the bay to insure that the conveyor is properly aligned with the semitrailer to be loaded, and can be fully extended. Because of this on-center positioning, when the conveyor is extended into the semitrailer, fork lift trucks, or other cargo vehicles cannot simultaneously access the trailer to load it, but must wait until the conveyor has been fully retracted into the storage position. Also, the take-off end of the conveyor cannot be moved laterally from one side of the trailer to the other to facilitate unloading.
Finally, the cantilevered type of loading conveyor generally does not include any mechanism to adjust the height of the discharge end. Since the height of semitrailers and truck beds varies, the elevation of the discharge end of the conveyor cannot be maintained at a convenient height for unloading.